Hydrodynamic characteristics of a four-compartment periodic anaerobic ba ed reactor

Periodic anaerobic baffled reactor (PABR) is a novel reactor based on the design concept of anaerobic baffled reactor (ABR). Residence time distribution (RTD) studies on both clean and working reactors at the same hydraulic residence time (HRT) of 2 d were carried out to investigate the dead spaces and mixing patterns in PABRs at different organic loading rates (OLRs) in various switching manners and frequencies.The results showed that the fraction of dead space in PABR was similar to that in ABR,which was low in comparison with other reactor designs.Dead space may be divided into two categories,hydraulic and biological.In RTD studies without biomass,the hydraulic dead space in the PABR run in an"every second"switching manner with T=2 d was the lowest whereas that in the PABR run in a T=∞(ABR) switching manner was the highest.The same trend was obtained with the total dead space in RTD studies with biomass no matter what the OLR was.Biological dead space was the major contributor to dead space but affected decreasingly at higher OLR whichever switching manner the PABR run in.The flow patterns within the PABRs were intermediate between plug-flow and perfectly mixed under all the conditions tested.     

旅游客源分析兼论宜州市旅游客源条件

本文分析了影响旅游资源的开发因素之一──客源的形成条件，在此基础上对广西宜州市旅游资源的客源条件进行了分析．     

2018年冬季南京重霾污染特征及气象因素分析

2018年11月底—12月初南京及周边地区发生一次大范围持续性霾污染,利用南京市空气质量监测资料、颗粒物成分逐时观测资料、南京站探空资料等,结合天气学诊断分析、后向轨迹模拟和聚类分析等方法,分析此次重霾事件的污染特征和气象因素.结果表明,此次重霾事件具有峰值浓度高、持续时间长、波动较明显等特点.污染时段PM_2.5浓度变化分为3个阶段,平均浓度为114.7 μg·m^-3,整体达到中度污染.重霾期间南京市大气环境处于富氨条件,颗粒物整体偏酸性,移动源排放比重高于固定源,PM_2.5主要成分的存在形式为硫酸铵、硝酸铵和其他硝酸盐.本次重霾事件中气象条件对污染物的输送和累积影响显著,在PM_2.5浓度极端事件发生期间,均有各气象要素与PM_2.5浓度同步变化.高PM_2.5浓度与对流层低层增暖增湿、弱的西南风相对应.重霾事件的主要天气成因是冬季东部地区出现大面积稳定且持久的均压场,南京及周边地区近地面中高层污染物主要由西北和华北地区输送而来,低层污染物主要来自于本地源排放累积.动力条件和热力条件的相互配合,近地面受高压影响形成暖平流逆温层,且易形成下沉气流,使重霾天气持续发展.     

絮凝剂产生菌的筛选及其培养条件优化

从活性污泥中筛选到１３株产絮凝剂的菌株,经复筛得到１株具有较高絮凝活性的菌,初步鉴定为假单胞菌ＰｓｅｕｄｏｍｏｎａｓｓｐＧＸ４－１。该菌产絮凝剂的适宜培养基及培养条件如下:葡萄糖２％,酵母膏０.４％,ＫＨ２ＰＯ４０.４％,ｐＨ７．０～９．０,３０℃,２００ｒ／ｍｉｎ,摇床培养２～３ｄ。产生具有高絮凝活性的絮凝剂,对高岭土悬液的絮凝率最高可达９２.７％      

Formation of multiple trimethylsilyl derivatives in the derivatization of 17α-ethinylestradiol with BSTFA or MSTFA followed by gas chromatography-mass spectrometry determination

N,O-bis(trimethylsily)trifluoroacetamide (BSTFA) and N-methyl-N(trimethylsily) trifluoroacetamide (MSTFA) are common derivatization reagents used in the GC-MS analysis of estrogen steroids such as estrone (E1) and 17(-ethinylestradiol (EE2). In this study, three trimethylsilyl (TMS) steroid derivatives, mono-and di-trimethylsilyl EE2 and mono-trimethylsilyl E1, were observed during the derivatization of EE2 with BSTFA or MSTFA and/or GC separation. Factors influencing the production of multiple TMS derivatives and their relative abundance were examined. It was found that both methanol and bisphenol A competed with estrogenic esteroids when reacting with silylation reagents, and thus affected the formation of TMS derivatives and their relative abundance in the derivatization products. Methanol was found to be more reactive than bisphenol A with the BSTFA reagent. None of the three solvents tested in this study could prevent the generation of multiple TMS derivatives during the derivatization of EE2 with BSTFA, followed by GC analysis. A similar result was observed using MSTFA as the derivative reagent followed by GC analysis. Thus, the suitability of BSTFA or MSTFA as the derivatization reagent for the determination of E1 and EE2 by GC-MS, under the conditions reported here, is questionable. This problem can be solved by adding trimethylsilylimidaz (TMSI) in the BSTFA reagent as recommended, and the performance of the method has been proved in this study.     

郑汴路不同运营路段路旁土壤重金属分布及污染分析

选择运营时间不同的杏花营和圃田路段分别布设1800 m长的采样断面,按距离路基远近不同布设土壤采样点38个,对照采样点2个,在距路基25 m处挖掘土壤剖面2个,共采集土壤样品50个.在室内试验的基础上,对路旁土壤重金属(Pb、Cd、Ni、Cu、Zn、Cr)空间分布特征与污染状况进行了研究.结果表明,公路两侧300 m范围内的土壤重金属含量明显高于对照区和中国潮土背景值,尤其土壤中Cd、Cr和Pb积累明显.路北土壤重金属含量高于路南.对于运营时间长的杏花营断面,土壤重金属含量高于圃田断面.大多数重金属在土壤中的含量随离公路距离的增加在距路基10～50 m处出现积累峰值,然后逐渐下降,在300 m附近接近于对照值.重金属主要累积在土壤深0～40 cm范围内.杏花营路段两侧200 m范围内为重金属轻度污染带,200～300 m之间为警戒带.圃田路段北侧30 m范围内为轻度污染带,30～200 m为警戒带,200～300 m为清洁带;而其南侧15 m范围内为轻污染带,15～80 m为清洁带,80～300 m为警戒带.     

三峡库区次级河流回水区环境因子对藻类生长影响的模拟实验研究

从三峡库区次级河流139m回水区采集水样,选用L9(34)正交表进行藻类培养试验,以Chla最大浓度作为指标选择适合藻类生长的适宜条件.结果表明,当控制水样温度为20℃、光照为8000lx、活性磷酸盐和溶解无机氮浓度分别为2.86μmol·L-1、85.71μmol·L-1时藻类生长最好;磷为限制该水域藻类生长的营养元素,藻类生长氮磷元素适宜摩尔比约为30:1.在适宜生长条件下,对数期藻细胞比生长率达到1.03d-1,稳定期Chla最大浓度达到110mg·m-3.     

Determination of the performance limits of flame arresters at increased oxygen concentrations

This investigation shows how an increased oxygen concentration influences the performance limits of crimped ribbon deflagration flame arresters at elevated pressures. An evaluation of the maximum experimental safe gap (MESG) as reliable criterion for describing the performance limits under non-atmospheric conditions is given. Measurements of MESGs and flame arrester performance tests were performed. Various fuel/oxygen/air mixtures containing ethylene and propane were used as testing gases. Former studies on the pressure dependence and the influence of oxygen on the MESG were initially confirmed. Furthermore, performance tests using a commercial deflagration flame arrester revealed that such a flame arrester may prevent flame transmission also at non-atmospheric conditions within a limited range. For various oxygen concentrations the performance limits were reached at the same MESG. Hence, it can be assumed that a flame arrester possesses a device- and fuel-specific maximum experimental safe gap for a specific gas mixture in different concentrations and at different pressures. This performance-related maximum safe gap can be used as a parameter for estimating and describing the performance limits of a flame arrester. It offers an attempt to simplify the testing and qualification of deflagration flame arresters for non-atmospheric conditions.     

北京市2015年森林植被区PM10质量浓度时空变化特征

以北京市大兴区南海子公园植被区与亦庄非植被区为研究对象,对比分析了植被区与非植被区PM₁₀质量浓度日变化、月变化特征及典型天气条件下的变化.结果表明：PM₁₀浓度的日变化趋势基本相同,呈典型的双峰曲线,春、夏季的峰值出现在9：00-10：00和18：00-19：00,秋、冬季的峰值出现在8：00-9：00和18：00-19：00,且秋、冬季PM₁₀浓度高于春、夏季;植被区与非植被区的PM₁₀月变化趋势基本一致,植被区PM₁₀浓度低于非植被区,且2月份PM₁₀浓度最大;各季节优良天气排序为夏季（42.60%）> 秋季（31.10%）> 春季（26.43%）> 冬季（15.17%）,中度及以上污染天气所占比例排序为冬季（55.52%）> 春季（27.57%）> 秋季（17.77%）> 夏季（3.58%）;PM₁₀浓度随降雨强度的增加呈减小的变化趋势,雨前12 h的PM₁₀浓度均值表现为植被区（106.43 μg·m^-3）<非植被区（157.39 μg·m^-3）,雨后12 h的PM₁₀浓度均值表现为植被区（50.96 μg·m^-3）>非植被区（38.41 μg·m^-3）;PM₁₀浓度随风速的增大呈减小的变化趋势,风后12 h的非植被区PM₁₀浓度削减率均值是植被区的1.23倍,且PM₁₀浓度削减率均处于较高水平;PM₁₀浓度随空气湿度的增大呈增大的变化趋势,随温度的升高呈减小的变化趋势.研究结果对进一步治理和控制北京市大气污染有参考价值.     

超磁分离技术在生态补水工程中的应用

生态补水是做好水资源综合治理与保护体系中不可或缺的一个内容,针对巢湖流域某生态补水工程超磁分离工艺的应用进行研究。该工程从巢湖取水经磁混凝处理后,出水主要指标稳定到达《地表水环境质量标准》(GB 3838-2002)的Ⅲ类标准,成为了景观河道的有效清洁水源补给,改善了生态环境。